In one method of manufacturing electrical terminals, the terminals are stamped and formed from metal strip and are attached to a carrier strip. The carrier strip is useful for strip feeding the terminals through successive manufacturing operations. One of the necessary manufacturing operations involves plating, i.e., electroplating the electrical contact surfaces of the strip fed terminals with a contact metal, usually noble metals or noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating will enhance conductivity of the terminals. The high cost of the metals has necessitated precision deposition of these metals on the contact surfaces of the terminals, and not on the remaining surfaces of the terminals.
Plating apparatus, also known as a plating cell, includes an electrical anode, an electrical cathode comprised of the strip fed terminals, and a plating solution, i.e., an electrolyte of metal ions. A strip feeding means feeds the strip to a strip guide. The strip guide guides the terminals through a plating zone while the terminals are being plated. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode through the plating solution to the cathodic terminals. The metal ions deposit as metal plating on those terminal surfaces in contact with the plating solution.
U.S. Pat. Nos. 4,690,747, 4,384,926, 4,427,498 and 4,555,321, owned by this assignee, disclose plating apparatus in which the interior surfaces of strip fed terminals are plated by supplying plating fluid through nozzles and over associated anode extensions or assemblies that are mounted for reciprocation into and out of the interiors of terminals. In effect, each anode extension, nozzle and terminal is a plating cell, and each apparatus comprises a plurality of plating cells. In the first three patents above, the anode extensions are mounted within their associated nozzles. In the fourth patent above, the anode extensions are mounted separately and apart from the nozzles and enter the terminals from a different direction than that of the plating fluid.
The apparatus disclosed in the four referenced patents are designed to be used with stamped and formed terminals, wherein the contact zone is located on the inside surface of a formed terminal. Each apparatus is comprised of an assembly of conductive and dielectric parts, with most of the parts mounted for rotation on a stationary axis. Each apparatus consists generally of a mandrel that is continuously rotated as strip fed electrical terminals are continuously fed to the mandrel, partially wrapped against it and exited from it. The mandrel is turreted with a plurality of nozzles distributed about its axis of rotation. Anodes are associated with the nozzles and are mounted for movement into and out of the interiors of the terminals that are against the mandrel. A conduit supplies plating solution under pressure through the nozzles and upon the anodes. The nozzles inject plating solution into the interiors of the terminals in which the anodes are received. A source of electrical potential supplies an electrical current flow from the anodes, through the plating solution and into the interiors of the terminals in which the anodes are received. In essence, each mandrel has a plurality of plating cells distributed about its axis of rotation.
Anode members or anode extensions are mounted within the assembly such that they can be moved into and out of the contact zone inside a formed terminal. The conductive anode members are either continually in mechanical engagement and electrical contact with or brought into electrical contact with an electrically charged member just prior to moving the anode member inside the terminal to selectively plate the contact zone.
In the '926, '498 and '321 patents, the anode members are held against the charged member under tension by using either a spring in the anode extension member itself or by spring loading the anode extension members against a conductive plate of the apparatus or both. The anode members are then moved into and out of aligned terminal members by hydraulic, mechanical or a combination of means.
In the '747 patent, the apparatus is provided with both a means for assuring an essentially uniform current to each of the cells and a camming means to positively move the anode means into and retract the anode means from engagement with the terminal.
When plating electrical terminals in apparatus such as those described above, it is important that the electrical terminals be properly aligned with the anode means before the anode means is moved into the terminal particularly to avoid damaging the anode means or plating apparatus. It is desirable, therefore, to have a means whereby an anode means can remain in its retracted position when there is misalignment of the terminal or a damaged terminal is present on the mandrel. Furthermore it is desirable that the non-insertion of one anode means does not damage either the anode means, the apparatus or interrupt the plating operation.